Share 'banner pricing'

Can any one help me with banner pricing?  I need to print a banner 2.5' by 14 feet. on Coral 13oz banner material, simple art, about 30% ink coverage. Are most of you guys using a square foot pricing? and if so, do you start to discount that price when you get into large banners? I am looking online and see prices all over the map. Thanks for any help Matt pictureworks